Abstrict A flow meter has a body, an inlet operatively connected to a source
of gas, and an outlet. A valve for opening and closing the outlet
is provided which includes a valve seat, a valve shaft movable axially
relative to the valve seat and a valve member on the valve shaft.
The valve member movable by axial translation of the valve shaft
between a first position in which the valve member engages the valve
seat to close the outlet and a second position in which the valve
member is spaced from the valve seat to allow gas to pass through
said outlet. The flow meter further includes a sensor which senses
the position of said valve member relative to said valve seat and
generates a signal indicative of said position. In one embodiment,
the sensor comprises an infrared light emitter and an infrared photo-detector
positioned on opposite sides of the valve member, which is preferably
conical. Depending on the axial position of the valve member, the
amount of light which reaches the photodetector changes. In another
embodiment, the valve shaft is operable connected to a potentiometer
which is responsive to the rotational position of the valve shaft,
and hence the axial position of the valve member. In a third embodiment,
a magnet is placed about the valve shaft, and a magnetic field detector
is placed within the magnets magnetic field. The sensor is responsive
to the position of the magnet and hence the position of the valve
member.
Claims We claim:
1. A flow meter having a body, an inlet operatively connected to
a source of gas, an outlet, and a valve for opening and closing
the outlet, the valve including a valve seat, valve shaft movable
axially relative to said outlet and a valve member provided on said
valve shaft, said valve member movable between a first position
in which said valve member engages said valve seat to close said
outlet and a second position in which said valve member is spaced
from said valve seat to allow gas to pass through said outlet; said
flow meter further including a sensor which senses the position
of said valve member relative to said valve seat and generates a
signal indicative of said position; said sensor comprising a potentiometer
having a rotatable shaft, said valve shaft being coupled to said
potentiometer shaft such that said valve shaft will translate axially
without moving said potentiometer, said potentiometer generating
a signal indicative of the rotational position of said valve shaft,
and hence of the setting of the valve member.
2. A flow meter having a body, an inlet operatively connected to
a source of gas, an outlet, and a valve for opening and closing
the outlet, the valve including a valve seat, valve shaft movable
axially relative to said outlet and a valve member provided on said
valve shaft, said valve member movable between a first position
in which said valve member engages said valve seat to close said
outlet and a second position in which said valve member is spaced
from said valve seat to allow gas to pass through said outlet;
said flow meter further including a sensor which senses the position
of said valve member relative to said valve seat and generates a
signal indicative of said position;
said sensor comprising an annular magnet fixed to said valve shaft
at a desired axial location along said valve shaft and a magnetorestrictive
sensor;
said magnet producing a magnetic field, said magnetorestrictive
sensor being positioned externally of said flow meter and within
said magnetic field, said magnetorestrictive sensor generating an
output indicative of the strength of said magnetic field for a specified
location in the setting of the said shaft, wherein, when said valve
shaft and valve member translate axially, the position of the magnet,
and hence the magnetic field, move relative to magnetorestrictive
sensor, the signal generated by the magnetorestrictive sensor being
indicative of the setting of the position of the valve shaft, and
hence the valve member.
3. A flow meter having a body, an inlet operatively connected to
a source of gas, an outlet, and a valve for opening and closing
the outlet, the valve including a valve seat, valve shaft movable
axially relative to said outlet and a valve member provided on said
valve shaft, said valve member movable between a first position
in which said valve member engages said valve seat to close said
outlet, and a second position in which said valve member is spaced
from said valve seat to allow gas to pass through said outlet, said
flow meter further including a sensor which senses the position
of said valve member relative to said valve seat and generates a
signal indicative of said position;
said sensor comprising an emitter which produces an infrared light
beam and photo detector which detects infrared light, said emitter
and detector being positioned in said meter on opposite sides of
said valve member, such that said detector can detect light transmitted
perpendicularly across said valve member by said emitter, said valve
member having a tapered surface such that as said valve shaft, and
hence said valve member translate axially relative to said valve
seat, the quantity of light emitted by said emitter which reaches
said detector varies, said detector generating an output signal
indicative of the amount of light which impinges on said detector,
and provides an indication of the position of said valve member;
a microprocessor including a data storage device, said microprocessor
being operatively connected to said sensor to receive said signal
generated by the sensor, said microprocessor including means for
converting said signal from said sensor into information indicative
of the setting of the flow meter valve shaft through passage of
the infrared light beam perpendicularly there across, and wherein
said microprocessor stores the information in said storage device.
4. The flow meter of claim 3 wherein said microprocessor includes
a comparator and an alarm, said microprocessor storing prescription
information in said data storage device, said comparator comparing
said setting of the flow meter against said prescription information;
said comparator generating a signal if said information does not
correspond to said prescription information, said alarm being responsive
to said comparator signal to activate said alarm when said setting
information does not correspond to said prescription information.
5. The flow meter of claim 4 herein said microprocessor includes
communication means, said communication means being operable to
transmit the information store in the data storage device to a remote
location.
Description CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
This invention relates to a therapeutic gas flow meter and, in
particular to a flow meter which monitors the flow setting and flow
adjustments made by a patient or user of therapeutic gas.
Generally, a patient with a pulmonary breathing disorder or oxygen
deficiency is required to breath oxygen provided from a source of
oxygen to increase the level, or amount of oxygen they breath in
from the atmosphere. The patient is given a prescription that indicates
the concentration of oxygen, the flow or volume requirement of oxygen,
and the use of the oxygen, for example, the hours per day of oxygen
delivery. In some cases, the prescription will include the precise
hours of the day the patient is to receive the oxygen therapy. For
example the patient's prescription may call for two liters of oxygen
per minute for two hours during the day and eight hours at night.
Or, in some cases, the prescription may call for four liters of
oxygen per minute for twenty-four hours a day. Usually the prescription
is based upon oxygen requirements established in a controlled setting,
such as at a hospital during hospitalization. The prescription is
continued at home after the patient is discharged from the hospital.
Delivery of oxygen therapy at home should correspond to the prescription
developed in the hospital. Failure to comply with the prescription
could be harmful to the patient or less beneficial than planned.
Oxygen concentrators have been developed and commercialized to
provide the delivery of near pure oxygen to the individual patient
to satisfy medical needs. These concentrators can be small and portable.
However, once the patient leaves the controlled setting of the hospital,
it is difficult to monitor the patient's use of the oxygen to ensure
that he is complying with the prescription. An important part of
a patient's therapeutic gas prescription is the flow amount or rate.
Thus, it is important to know at which level the patient has set
his therapeutic gas meter and equally important to know when and
to what amount an adjustment is made.
The preferred therapeutic gas source generally is an oxygen concentrator.
Other therapeutic gas sources can of course be used. The gas source
normally uses an adjustable flow meter having a ball indicator so
that the user can read the flow rate. Two common flow meters found
in oxygen concentrators are those manufactured by Key Instruments
of Trevose, Pa., under Part #FO43 and by Dwyer Instruments of Michigan
City, Ind., under Part #59-700360-00. A typical flow meter 1 is
shown in FIGS. 1 and 2. The flow meter 1 includes a meter body 3
having an inlet port 5 and outlet port 7 and a Thorpe Tube 9 between
the inlet and outlet through which the gas flows. An indicator ball
11 floats in the Thorpe Tube 9 and is elevated or floated in the
Thorpe Tube by the flow of gas through the tube 9. The level to
which the ball 11 is raised is indicative of the flow rate of gas
through the meter. An indicating scale 13 is provided to allow a
user to read the flow rate. A user adjustable metering valve 15
is operated by a knob 17 to alter the flow through the meter. Typically,
the valve 15 is a needle valve, and includes a needle portion 19
which extends forwardly of a shaft 20 and into the throat 21 of
the outlet 7. The valve shaft is threaded, as at 23. The threads
23 are received in an internally threaded boss 25. An O-ring 27
is provided to prevent gas from escaping out through the boss. Thus,
as can be appreciated, by rotating the knob 17 the needle 19 moves
axially to be inserted into, or pulled away from, the throat 21
to open or close the outlet 7.
Operation of this type of flow meter is simplistic and well known
in the art. Therapeutic gas enters inlet port 5 travels through
Thorpe Tube 9 causing the indicator ball 11 to rise to a level which
is proportional to the amount of therapeutic gas flow which exits
at the outlet port 7. When the user desires to control the flow
of therapeutic gas the patient adjusts the user adjustable metering
valve knob 17 alters the degree to which the throat 21 is open,
to decrease or increase the therapeutic gas flow to the desired
level as indicated by the alignment of the indicator ball 11 on
the indicating scale 13. Typically the user rotates the user adjustable
metering valve knob 17 in a clockwise direction to restrict the
flow of therapeutic gas to a lesser amount and likewise the user
may adjust the metering valve knob 17 counter-clockwise for a greater
amount of therapeutic gas flow.
Flow information is normally only available by reading the ball
indicator on the flow meter. When it is desired to obtain flow information
via electronic means an electronic flow sensing means must be added
to the meter. Flow sensing means and the use of flow sensors to
monitor the flow of a gas through a meter are known. However, we
know of no sensors which monitor the setting of the meter. When
using an oxygen concentrator, it may be necessary to monitor the
valve setting independently of the flow rate. In these cases it
is necessary to not only monitor flow settings but also to log into
memory flow setting data to communicate this data to a care giver.
BRIEF SUMMARY OF THE INVENTION
In accordance with the invention, generally stated, a flow meter
is provided with a sensor to measure the setting of the flow meter,
as compared to the flow rate of gas flowing through the flow meter.
The flow meter has a body, in inlet operatively connected to a source
of gas, an outlet, and a valve for opening and closing the outlet.
The valve includes a valve seat, a valve shaft movable axially relative
to the outlet and a valve member on the valve shaft. The valve member
is movable between a first position in which the valve member engages
the valve seat to close the outlet and a second position in which
the valve member is spaced from the valve seat to allow gas to pass
through the outlet. The sensor generates a signal indicative of
the position of the valve shaft and hence the valve seat.
In accordance with one aspect of the invention, the sensor comprises
an emitter which produces an infra-red light beam and a photodetector
which detects infra-red light. The emitter and detector are positioned
in the meter on opposite sides of the valve member such that the
detector can detect light transmitted by the emitter. The valve
member has a tapered surface such that, as the valve shaft, and
hence the valve member translate axially relative to the valve seat,
the amount of light emitted by the emitter which reaches the detector
varies.
In another aspect of the invention, the sensor comprises a potentiometer
have a rotatable shaft which is coupled to the valve shaft. The
connection between the valve shaft and the potentiometer shaft allows
the valve shaft to translate axially without moving the potentiometer.
This will allow the potentiometer to be fixed or mounted, for example,
to a circuit board. The potentiometer generates a signal indicative
of the rotational position of the valve shaft, and hence of the
setting of the valve member.
In another variation, the sensor comprises an annular magnet fixed
to the valve shaft at a desired axial location along the valve shaft
and a magnetorestrictive sensor which detects the magnitude of the
magnetic field produced by the magnet. The magnetorestrictive sensor
is positioned externally of the flow meter and within the magnetic
field. As the valve shaft and valve member translate axially, the
position of the magnet, and hence the magnetic field move relative
to the magnetorestrictive sensor. Therefore, the magnitude of the
field detected by the magnetorestrictive sensor will vary in accordance
with the position of the magnet, and hence the valve shaft.
In accordance with another aspect of the invention, the flow meter
includes a microprocessor having a data storage device which stores
the signal generated by the sensor as well as the prescription information.
The microprocessor is provided with a comparator and an alarm. The
comparator compares the real time data to the prescription information,
and if the real time data does not correspond to the prescription,
the alarm is activated. The flow meter can also be provided with
communication means, such as a modem, for example. The communication
means can be activated at the same time the alarm is activated to
alert a care giver of the out-of-prescription condition of the flow
meter. The communication means can also be used to transmit the
information stored in the data storage device to a desired location,
so that the care giver can review the patient's compliance with
the prescription.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a perspective view of a prior art flow meter;
FIG. 2 is a cross-sectional view of the prior art flow meter;
FIG. 3 is a cross-sectional view of a flow meter of the present
invention;
FIG. 4 is an enlarged cross-sectional view of one embodiment of
a setting sensor of the present invention;
FIG. 5 is an enlarged front plan view of the setting sensor of
FIG. 4;
FIG. 6 is an electrical schematic of the setting sensor of FIG.
4;
FIG. 7 is a graph of the electrical signal output by the setting
sensor of FIG. 4;
FIG. 8 is a schematic cross-sectional view of an alternative setting
sensor of the invention which uses a potentiometer;
FIG. 9 is a schematic cross-sectional view of a third alternative
setting sensor of the present invention which uses a magnetorestrictive
element;
FIG. 10 is a perspective view of the magnetorestrictive element
of FIG. 9; and
FIG. 11 is a block diagram of the sensors of the present invention
and the connection of the sensor to a microprocessor.
Corresponding reference numerals will be used throughout the several
figures of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The following detailed description illustrates the invention by
way of example and not by way of limitation. This description will
clearly enable one skilled in the art to make and use the invention,
and describes several embodiments, adaptations, variations, alternatives
and uses of the invention, including what we presently believe is
the best mode of carrying out the invention.
A first illustrative embodiment of a flow meter 101 of the present
invention is shown in FIGS. 3-5. The flow meter 101 is substantially
similar to the flow meter 1 and includes a body 103 having an inlet
105 an outlet 107 and a Thorpe Tube 109 between the inlet and
outlet. A float ball 111 and indicator marks 113 are provided for
a visual determination of the flow rate. As with the flow meter
1 the flow meter 101 includes a needle valve 115 operable by a
knob 117 to increase or decrease the size of the throat 121 into
the outlet 107. The valve 115 includes a valve shaft 116 which steps
down at 118 to a needle portion 119 and as before, the needle portion
is received in the throat 121 of the outlet 107. As can be appreciated,
the shape of the throat 121 corresponds to the shape of the sloped
portion 118 of the shaft 116. Thus, the throat 121 defines a seat
for the valve 115 and the sloped portion 118 of the shaft 116 defines
a valve element which, when its valve member 116a is engaged with
the valve seat (throat 121), closes the outlet 107.
To monitor or sense the setting of the valve, the meter 101 is
provided with an infra-red emitter 123 and an infra-red photodetector
125. The infra-red emitter 123 is one such as is commonly available
from Digi Key of Thief River Falls, Minn., under part #LT1028. The
infra-red photodetector 125 is also commonly available from Digi
Key as part #LT1030. The emitter 123 generates an infra-red light
beam 127 which is detected by the photodetector 125. The photodetector
125 in turn, generates an electrical signal indicative of the amount
of light which impinged on the detector. The emitter 123 and detector
125 are positioned on opposite sides of the valve shaft 116 such
that as the knob 117 is turned, the transition area 118 of the valve
115 will move across the path of light. As can be appreciated, as
the valve is closed, the amount of light 127 which will reach the
detector 125 will decrease, the light being deflected off the transition
portion 118 of the valve 115 as seen in FIG. 5. Conversely, when
the valve is opened, the amount of light which reaches the detector
125 will increase.
In operation the position of mechanical metering valve shaft 116
is proportional to the flow setting selected by the user. Both the
infra-red emitter 123 and the infra-red photodetector 125 are embedded
into the flow-meter assembly 101 or mounted within the flow meter
assembly. Thus, when the valve shaft 116 is fully retracted (i.e.,
the throat 121 is fully open), a large amount of infra-red light
will reach the photodetector 125. This large amount of infra-red
light beam transmission would indicate flow settings correspond
to abnormal therapeutic gas settings. The user would adjust the
user adjustable metering valve knob 117 clockwise for the desired
level of therapeutic gas flow as prescribed by physician. The output
of the detector 125 can be operatively connected to an alarm, so
that when the too high or too low flow levels are detected, the
alarm can be sounded to alert the user to change the flow setting.
As the mechanical metering valve shaft 116 moves from left to right
(with reference to FIGS. 3 and 4) to close the valve, the infra-red
light beam 127 becomes blocked thus reducing the amount of infra-red
light beam 127 detected at infra-red photodetector 125. Thus, the
flow setting made by the user affects the position of the mechanical
metering valve shaft 116 and causes corresponding infra-red light
beam 127 to be partially blocked. The amount of light which reaches
the detector 125 is proportional to the flow setting.
FIG. 6 is a simple schematic of the emitter 123 and detector 125
of the sensor. As shown, the emitter 123 and detector 125 include
associated power sources 129 and 131 and resistors 133 and 135.
The detector 125 also includes a voltage output 137 through which
the signal generated by the detector is transmitted. The power supplies
129 and 131 are +5 VDC sources, and may be a single source for both
the emitter and the detector. The resistor 133 is preferably a 332.OMEGA.
resistor and serves to limit the amount of current flowing through
the infra-red emitter 123. The resistor 135 is preferably a 249.OMEGA.
resister, and in conjunction with infra-red photodetector 125 provides
a voltage divider network that creates an output voltage at 137
which is proportional to the amount of light received at infra-red
photodetector 125.
To ensure a constant level of brightness from emitter 123 a constant
current source, such as Part #TL43 1 available from Motorola and
associated circuitry, could be substituted for the resistor 133.
It is possible to provide an additional infra-red photodetector
to allow for a calibration check of the system, thereby assuring
a constant brightness or light level from infra-red emitter 123.
Then any change in the system dynamics from the second infra-red
photodetector would be evident as a measurable change in the normal
difference of the voltage output of the devices. This could result
in activation of an alarm which would notify the patient and/or
the caregiver that the flow is in an out-of-tolerance situation.
FIG. 7 is a graph of the unamplified voltage output produced by
the system schematically shown in FIG. 6. This output voltage could
be processed using commonly available electronic means to provide
a more linear output which could be utilized for further processing
to achieve other functions, such as flow setting alarm levels. One
method of processing the voltage output by the detector 125 would
be to incorporate a microprocessor, such as Motorola of Phoenix,
Ariz., Part #MC74HC05P6.
A second therapeutic gas electronic flow meter/monitor 201 is shown
in FIG. 8. The flow meter/monitor 201 is based upon the basic design
of the meters 1 and 101. However, the outlet 207 is modified, as
will be discussed. The flow meter/monitor 201 uses a potentiometer
223 as the sensor to monitor the setting of the valve 215. Operation
of the flow meter/monitor 201 is similar to the operation of a typical
flow meter 1 however the outlet port 206 has been modified to a
generalize "S" shape to allow the valve shaft 216 to be
extended. The valve shaft 216 exits through a shaft exit 225 and
an O-ring 227 is provided around the shaft 216 to prevent the gas
from escaping through the shaft exit 225. The gas exit 207 is formed
as an "L" depending from the shaft exit 225 and is positioned
after the throat 221 of the valve 215. Thus, the therapeutic gas
will exit through port 207 after it passes through the throat 221.
A shaft coupler 229 connects the valve shaft 216 to a shaft 231
of the potentiometer 223. The coupler 229 is connected to the end
of shaft 216 such that rotation of the shaft will rotate the coupler,
so that the rotational position of the shaft 216 can be mechanically
transmitted to the potentiometer 223. However, the connection between
the coupler 229 and the shaft 216 allows for axial translation of
the shaft 216 relative to the coupler 229 so that as the shaft
translates axially, the coupler will not move axially. Such a connection
can be made, for example, using a key and slot arrangement, wherein
a slot is formed in the coupler and a key radiates from the shaft
to be received in the slot. This type of connection is desirable
if the potentiometer 223 is to be rigidly mounted to an electronic
circuit board or mechanical mounting bracket. The coupler 229 also
allows for perpendicular movement of the extended metering valve
shaft 216 so as not to interfere with normal operation of flow setting
by the user.
The potentiometer 223 provides an output in responsive to, and
indicative of, the position of valve shaft 216. The output can be
a analog voltage output. In some instances it is desirable to obtain
a digital output of flow setting. In such cases the use of an optical
binary encoder maybe substituted for setting potentiometer 223.
The optical encoder is available from Digi Key as Part #CT3003-ND.
This type of encoder would indicate sixteen flow setting positions.
Other encoders are available which will provide greater resolution
for example, 128 flow setting positions are available.
Still another method of measuring the flow setting is to use the
Giant Magnetoresistive Ratio (GMR) method of linear detection. Referring
to FIGS. 9 and 10 the flow meter 301 is based on the meter 1 previously
described. The mechanical metering valve shaft 316 preferably manufactured
out of stainless steel, has a donut shaped or annular magnet 323
fixed to the shaft 316 at a desired location along the shaft. The
magnet 323 extends around the shaft, as seen in FIG. 9. The donut
magnet 323 is one such as is available from McMaster Carr of Chicago,
Ill., Part #5902K55. A giant magnetoresistive ratio (GMR) sensor
325 such as is commonly available from Nonvolatile Electronics
Inc. of Eden Prairie, Minn., as Part #NV55B 10051 is installed
externally of the flow meter assembly 301 but within the magnetic
field generated from the donut magnet 323. The sensor 325 is preferably
installed on the top of the flow meter assembly 301 as shown in
FIG. 9.
In operation, the linear position of the magnet 323 relative to
the sensor 325 is proportional to the flow setting of the meter
301. That is, as the flow setting is changed by rotation of the
shaft 316 by rotation of the knob 317 the shaft 316 will move axially,
as described above. Because the magnet 323 is fixed relative to
the shaft 316 the position of the magnet 323 relative to the sensor
325 will change as the shaft 316 is rotated. This linear motion
moves the magnetic field of the donut magnet 323 relative to the
sensor 325. Thus, the local strength of the magnetic field at the
sensor 325 will change as the magnet 323 is moved. The magnetic
field measured by the giant magnetoresistive ratio (GMR) sensor
325 produces an output voltage which is linear and proportional
to the flow setting. The giant magnetoresistive ratio (GMR) method
produces an unamplified output voltage from about 0 to 250 mv proportional
to 0 to 6 LPM with an input voltage of 5 VDC when used with the
magnet described herein.
Proper calibration is achieved by the horizontal relationship between
the donut magnet 323 and the giant magnetoresistive ratio (GMR)
sensor 325. The amount of voltage output depends upon the magnetic
strength of the donut magnet 323 and the vertical distance between
the magnet 323 and the giant magnetoresistive ratio (GMR) sensor
325.
Those skilled in the art will recognize that other methods of flow
setting sensors may be incorporated in lieu of the potentiometer,
optical decoder, and magnetorestrictive sensor described above.
For example it may be desirable to incorporate a wheel assembly
which includes a magnet and a Hall effect sensor to count rotational
information and to use memory means to derive the flow setting information.
As another example, servo mechanisms could be utilized to obtain
flow setting information in response to mechanical flow metering
valve shaft rotation. It is common in the art, especially when the
therapeutic gas source being used is a liquid oxygen reservoir,
to incorporate a flow setting means that uses an adjustable orifice
or valve assembly which usually selects the flow of therapeutic
gas in 1/4 LPM increments. Such flow setting means utilize a series
of orifices and assume a relatively fixed operating pressure to
obtain the liter flow desired. Thus, it is possible and within the
scope of this invention to incorporate rotational flow setting means
such as the potentiometer method or optical method onto such an
adjustable orifice flow setting means and obtain the desired results
of this invention.
Turning to FIG. 11 the flow meter can be provided with an alarm
A, such as an audible or visible alarm which is responsive to the
signal generated by the sensor S. The sensor S may be any of the
above noted sensors. This may be accomplished through commonly available
componentry such as with the use of a microprocessor M available
from "Motorola" Part #MC74HC05P6 and which is provided
with a storage device 0 and a clock C. Additional memory storage
S and Clock C circuitry may be provided externally by microprocessor
M for more demanding applications of the present invention. The
microprocessor M is operable to store the prescription and the readings
from the setting sensors S and includes means for converting the
sensor signal into information indicative of the setting of the
flow meter. The alarm A could be utilized in different ways. For
example, if the patients prescription requires a flow setting during
a specified time period and the flow setting is adjusted outside
of the predetermined time period then all audio and/or visual alarms
can be made to alert a patient, or user, or caregiver, of the out
of compliance situation. This can be done, for example, by sending
the prescription information and the actual data, and a time reading
from the clock C to a comparator I. The comparator I will then compare
the real time data from the sensor to the prescription information
and date/time information. If the real time data does not correspond
to what the flow setting should be, based upon the prescription,
the comparator will generate a signal to activate the alarm. Also
communication means, such as a modem P, can be incorporated to alert
a remote station, such as the home care providers. Additional communication
of the alarm means may be accomplished through the use of a radio
frequency transmission and reception techniques (including pagers),
fiber optics techniques, etc.
The use of the microprocessor M and its associated memory storage
0 and date/time circuitry C allows for calibration of the flow meter
by software and communication means of the flow setting means and
method of flow setting means. This circuitry allows for preprogramming
of the alarm levels and the logic to be followed within the alarm
means. This circuitry also controls and coordinates the communication
means as previously mentioned. Furthermore this circuitry allows
the incorporation of historical data consisting of information about
calibration, alarm levels, date/time of alarms, and action taken.
Date/time of all flow settings and information concerning communications
that have taken place may also be logged. The use of the modem or
other communication means allows direct communication of historical
data from the point of care to a remote location to make the data
available for review by a physician or appropriate caregiver at
any desired time.
The flow meter could also be equipped with a flow sensor F which
would measure the actual flow of therapeutic gas being delivered.
This will allow the electronic circuitry incorporating microprocessor
and associated memory storage and date/time circuitry to provide
additional capability. Specifically, automatic calibration and periodic
calibration can be accomplished by comparing the measured value
from the flow sensor to the actual flow being measured. Calibration
and recalibration as described herein could also be controlled via
the communication means. Additionally if a leak in the therapeutic
gas patient delivery system occurs causing the actual flow delivered
to be different from that of the flow setting then the alarm means
including communication means could be activated.
In view of the above, it will be seen that the several objects
and advantages of the present invention have been achieved and other
advantageous results have been obtained. As various changes could
be made in the above constructions without departing from the scope
of the invention, it is intended that all matter contained in the
above description or shown in the accompanying drawings shall be
interpreted as illustrative and not in a limiting sense. Those skilled
in the art will recognize that modifications within the scope of
this invention may be made for example, just as there are various
methods to measure rotational movement which is proportional to
the flow setting there are also other methods to measure linear
motion which is proportional to the flow setting. A linear velocity
displacement transformer could readily measure the position of the
valve shaft. Additionally, capacitive proximity sensors could easily
measure linear motion proportional to the flow setting. |